I mean, what could possibly give that away? His chest-length beard that looks like he irons it every morning (or, more likely, has it ironed for him)? His deadly serious affinity for voodoo accoutrements like gris-gris bags and various other swampy spiritual charms? Or the fact that he’s cool with being internationally famous in great part for acting quite preposterously in a business known for being inherently preposterous? (Spinning, white sheep fur-covered Explorer-style guitars, anyone?)

A bona fide legend of both R&B and hard rock, Gibbons’ peculiar, reverential take on the funky, edge-living bluesman archetype has remained firmly in place for the last 43 years. In retrospect, it seems as much a sincere homage to the stalwart black blues and soul icons of his Texas youth as an exaggerated, slightly ironic caricature which belies his faith in the truth of blues and traditional American roots music.

Since 1970, when ZZ Top’s classic lineup of vocalist/guitarist Gibbons, bassist/vocalist Dusty Hill and drummer Frank Beard coalesced (out of the ruins of Gibbons’ promising psychedelic garage band The Moving Sidewalks and the rhythm section’s noteworthy combo American Blues), the group has become an iconic symbol of roadhouse Americana.

Often imitated, but never equaled, they’ve proven themselves one of the most unique and instantly recognizable power trios in the history of rock ‘n’ roll. Like the Ramones and AC/DC, the more ZZ Top changed over the years, the more they somehow stayed the same.

Their trio of “synthesizer” albums released from the early 1980s to the early ’90s (“Eliminator,” “Afterburner” and “Recycler”) saw the band’s raw, sexually charged and darkly humorous blues-rock morph unexpectedly into a bizarre brand of slickly (over)produced techno-pop that somehow allowed for stinging lead guitar licks that could have come from the stage of Austin’s famed nightclub Antone’s.

Yet those licks were nestled alongside the kind of robotic, massively gated percussion tracks that could only come from a drum machine — a decision spurred not only by desires of reaching a wider audience and expanding the group’s sonic palette but also by drummer Beard’s debilitating battles with both heroin and alcohol addiction.

By the time he’d kicked those nasty habits and rejoined the group (just in time to shoot some hysterically uncool promo videos for hits like “Sharp Dressed Man” and “Legs”), they’d become cartoonish megastars for the newly hatched MTV Generation — known as much for their attitude as their densely layered recordings and crowd-pleasing stage shows. Eventually, their record sales wavered as they moved from label to label, searching for folks able to promote a band with diminishing airplay, but which could still pack stadiums in all corners of the globe with fervent fans who never tired of the band’s sing-a-long hits and trademark dry wit.

These days, ZZ Top are elder statesmen of rock and blues who continue to dazzle audiences.

The band is currently touring behind their latest studio album (produced by controversial music biz mogul Rick Rubin, who has guided standout LPs for everyone from Beastie Boys and the Red Hot Chili Peppers to Neil Diamond and AC/DC).

“La Futura” is a fantastically enjoyable, impressive collection of angular, crunching guitar rave-ups and mournful ballads that succeeds wildly at blending the band’s initial approach to old-school grooves and off-the-cuff arrangements with Gibbons’ latter-day obsession with modern recording technology and the harsh tones of techno and industrial music.

(For proof of this hidden fascination, many moons ago, Billy waxed rhapsodic to me over wine and cake at our very own Gallery Espresso about his private love for the music of Nine Inch Nails and the Revolting Cocks, and in fact, he recently remixed a track off the new Depeche Mode album!)

Combined with the fact that Warner Bros. just released a massive 10-disc remastered box set of the group’s first 10 LPs (including long-unavailable original mixes of their earliest work that fans have clamored for), this week’s Johnny Mercer Theatre appearance is a hotly anticipated return to a town the band has played to roaring crowds several times over the course of their lengthy career.

As of press time, there were still good seats available, but something tells me they won’t last long.